Amongst several optical properties, refractive index is one of the most important criteria for selection of materials suitable for application in optics. One of the possible candidates for this purpose is plastic materials. Other than the essential properties like light transmission, transparency and refractive index, plastics are also known for their light weight. High refractive index is an important-property required for the manufacture of transparent synthetic resin as optical material. Transparent synthetic resin having high refractive index when used as optical products can be rendered thinner than material having low refractive index to give the same focal distance. The use of thin lenses contributes to reducing the volume of space occupied by lenses in optical assemblies, which can advantageously make an optical apparatus light weight and small sized.
Transparent composite materials are becoming increasingly important in applications ranging from protective coatings to optical communications. Optical materials are useful to control the flow and intensity of light. Examples of useful optical products include optical light fibers, light tubes, optical films including totally internal reflecting films, retroreflective sheeting, ophthalmic lenses. These monomers can be used in compositions to make light management films advantageously provide a cured composition having high refractive index. Even for applications such as liquid crystal displays, adhesives, magnifying lenses, binoculars, and telescopes requires monomers having high refractive index. High refractive index polymers have a wide variety of applications in dentistry, optical eyewear, holography, and microelectronics.
Optical products can be prepared from high index of refraction materials, including monomers such as high index of refraction (meth)acrylate monomers, aromatic based monomers, and other such high index of refraction monomers that are known in the optical product. The monomers can be cured or polymerized to take the form of a product capable of modifying or controlling the flow of light. The preparation of high refractive index monomers and their applications in optical articles are known in the prior arts.
Frunze, T. M et al. in Russian chemical bulletin 19 (1970), S. 183-184 discloses a process for preparation of 2-Allyl-4-phenoxyphenyl methacrylate, by the reacting of 2-allyl-4-phenoxyphenol with methacryloyl chloride, and their properties. Further Michael E. Wright (2010) reported a process for preparation of 3-{(4-phenoxyphenyl)}methyl methacrylate by treating 3-phenoxybenzyl alcohol with methacryloyl chloride.
U.S. Pat. No. 7,714,090 discloses a process for the production of a monoaryl(meth)acrylate compound by reacting the acryloyl compound with the aryloxy alcohol compound in a solvent in the presence of a catalyst. The invention also provides a process for preparation of a soft intraocular lens comprising the (meth)acrylate copolymer having a refractive index of 1.50 to 1.59.
U.S. Pat. No. 5,693,095 discloses an improved soft, foldable acrylic lens materials which are particularly suited for use as intraocular lens (IOLs), but which are also useful as other ophthalmic devices, such as contact lenses, keratoprostheses, and corneal rings or inlays. These materials contain only two principal components: one aryl acrylic hydrophobic monomer which is selected from the group consisting of 2-phenylethyl acrylate and 4-phenylbutyl methacrylate etc. and another hydrophilic monomer which is selected from the group consisting of 2-hydroxyethyl acrylate; 2-hydroxyethyl methacrylate, 2-N-ethylacrylate pyrrolidone, 2-hydroxy-3-phenoxypropyl acrylate etc. Further it comprises additional components, such as cross-linking, UV-light absorbing, and blue-light absorbing components. The copolymer of said patent has a refractive index of at least 1.50.
U.S. Pat. No. 5,290,892 discloses an intraocular lens comprising a copolymer with an elongation of at least 150%, wherein said copolymer is comprised of two monomers, the first of which is 1-phenylethyl acrylate at a concentration about 65 wt. % and the second of which is 2-phenylethyl methacrylate at a concentration of about 30 wt. %., and a copolymerizable cross-linking monomer such as 1,4-butanediol diacrylate having a plurality of polymerizable ethylenically unsaturated groups.
U.S. Pat. No. 5,891,931 relates to methods for preparing foldable acrylic, high refractive index ophthalmic device materials that contain a UV-absorbing chromophore and a benzoyl phosphine oxide photo-initiator which comprises activating the benzoyl phosphine oxide photo-initiator with a blue-light source.
U.S. Pat. No. 7,271,283 discloses a method of making a high refractive index monomer which comprises reacting an aromatic nucleophile with epichlorohydrin to form a disubstituted 2-propanol and reacting the disubstituted 2-propanol with an ethylenically unsaturated reactant to form a high refractive index monomer.
U.S. Pat. No. 8,378,046 provides pressure-sensitive adhesives having a refractive index of at least 1.50, comprising the inter polymerized reaction product of: (a) at least one (meth)acrylic acid ester monomer, (b) at least one monomer containing a substituted or an unsubstituted biphenyl group; and (c) at least one containing an acid functional monomer also provides process for preparation thereof.
WO 2009058513 discloses pressure-sensitive adhesive comprising the inter polymerized reaction product of: (a) at least one (meth)acrylic acid ester monomer, (b) at least one monomer containing a substituted or an unsubstituted carbazole group; and (c) at least one containing an acid functional monomer.
JP 2009280546 provides a new polymerizable di(meth)acrylate compound having a high refractive index and excellent transparency without problems of absorption in the ultraviolet region and fluorescence.
The catalyzed or uncatalyzed reaction of styrene oxide with phenol to form corresponding primary and secondary alcohols is disclosed by Cyrus O. Guss in J. Am. Chem. Soc., 1949, 71 (10), pp 3460-3462. A resin with a high refractive index and a high Abbe number composed of essentially sulfur-containing aromatic methacrylates. An optical material composed of said resin is provided especially for lenses, is reported in Journal of Applied Polymer Science, 2000 (76), pp 50-54.
Further, J. McGrath et al. in Polymer 2006(47), pp 4042-4057 discloses a novel, high-refractive index homo polymer produced by incorporating carbazole and phenol into the methacrylate monomer structure followed by recrystallization from methanol, produces a good yield of highly pure carbazole phenoxy functionalized methacrylate monomer. Subsequent free radical polymerization or UV photo polymerization of the functionalized methacrylate monomer, in addition to copolymerizations with methyl methacrylate, provided for high-refractive index materials well suited for lightweight optical applications.
Chehade, M. & Helder, M. J., (1997) in A review, ANZ Journal of Opthalmology, 25, 255-263 discloses development of foldable intraocular lens (IDLs) such as hydrogel, soft acrylic, silicon IOL and its clinical perspective.
High refractive index (RI) materials are extremely important in many optical applications. Polymers traditionally have relatively low refractive indices, but they can be raised to technologically useful values. L. Beecroft et al. have prepared RI tunable materials up to 1.68 using brominated and aromatic monomers in a copolymer synthesis method, wherein said copolymers are transparent in the technologically important near-IR, have high glass transition temperatures, and are good film formers which is disclosed in J. Macromolecular Science A 1997, 34 (4), pp 573-586.
Current high RI plastics include polyurethanes, polyesters, epoxy and episulfide resins. Most of the high RI plastics use thiourethane and episulfide chemistries with highly polarizable chemical moieties such as aromatics and sulfur. However, optical articles produced from these materials suffer from after-cure yellowing and strong odors released during lens processing. In addition, these monomers have inherently long production cycles due to prolonged curing times needed for maintaining optical homogeneity. Therefore, there is a need for monomers which offer fast cure, high RI, low color, and low odor when cured or upon cutting and grinding, while maintaining optical homogeneity and improved and efficient process for preparation thereof.
It is advantageous that, the novel monomers prepared according to the current process do not need any derivatization or treatment to polymerization to prepare material with high refractive index and excellent transparency property. In particular, the polymeric material prepared from the novel monomer can be used for making thinner optical articles than conventional used ones, with advantages of reduced volume of space and lightweight materials.
Further the aromatic based monomers of the present invention are more hydrophobic as compared to existing hydrophilic intraocular lens (IOLs). It is observed that the hydrophobic lenses which are generally made up of aromatic based materials are better at UV filtration than aliphatic materials based hydrophilic lens. Also surfaces of soft hydrophobic IOLs are smoother than those of soft hydrophilic IOLs and tailorable glass transition temperature is one of the benefits of the present aromatic hydrophobic monomers.